The Secret Service will send extra agents to protect Joe Biden in case he declares victory in the US presidential election.

The reinforcements will be assigned to Wilmington, Delaware, where the Biden campaign is headquartered at a riverfront convention centre, as votes continue to be counted in several key battleground states, sources told The Washington Post.

The agents were dispatched once learning the former vice-president planned to remain at the centre on Friday.

Biden could reach the 270 electoral votes needed to secure the presidency by Friday and make a victory speech from the convention centre.

Though Biden is getting added security, the Secret Service has yet to staff him with the level of protection given to presidents-elect, the report said. The Secret Service and the Biden campaign did not respond to a request for comment from the newspaper.

The Secret Service summoned a squad of agents to add to the protective bubble around Biden after his campaign alerted the Secret Service the Democratic nominee would continue utilizing a Wilmington convention centre at least another day and could make a major speech as early as Friday. 

Secret Service spokeswoman Catherine Milhoan declined to comment, stressing that the agency does not publicly discuss security planning for the president or candidates it protects. 

Dozens of agents have been providing security for Biden’s campaign at the Chase Center on the Riverfront convention center in Wilmington. 

The additional security for Biden that is expected to begin Friday doesn’t give him a full protective detail that accompanies a president-elect, but moves closer in that direction. It remains unclear when the Secret Service would provide that level of security for Biden should he win. 

The agency typically ramps up protection for a president-elect immediately after that person has been declared the winner by assigning a new raft of agents to the incoming president. Historically, that increase in protection has happened late into election night after one candidate has conceded and the other has given a victory speech. 

But this year’s race has been marked by drawn-out vote count and a flurry of unsubstantiated attacks by President Trump on the integrity of the election. 

If Biden is considered the clear winner and Trump does not concede, the Secret Service could wait under agency protocol until the electoral college meets in mid-December to certify the vote results before officially treating Biden as the president-elect. 

But Secret Service would likely feel duty-bound to ramp up protection before then, a former agent said. 

The agency has only faced such a decision once before: in the contested 2000 presidential race between Republican George Bush and then-Vice President Al Gore. 

For 36 days, there was no official president-elect as the two sides were locked in a recount over votes in Florida and then a legal fight that went to the Supreme Court. 

During that time, the Secret Service maintained the status quo, keeping the vice-presidential protective detail with Gore and continuing to protect Bush as a major candidate.